1. Technical Field
The present invention relates to a multi-cylinder engine and more particularly it concerns a multi-cylinder engine capable of inhibiting an EGR cooler from being damaged and at the same time making the EGR cooler compact.
2. Earlier Technology
There is a conventional example of this multi-cylinder engine which, on the assumption that a direction where a crank shaft spans is taken as a front and rear direction and that a widthwise direction of a cylinder head perpendicular to the front and rear direction is deemed as a lateral direction, comprises the cylinder head having one lateral side surface to which an intake-air distributing passage wall is attached and having the other lateral side to which an exhaust-gas converging passage wall is attached, the exhaust-air converging passage wall having an interior area communicated with an interior area of the intake-air distributing passage wall through an EGR cooler, as well as the present invention.
The multi-cylinder engine of this type has an advantage of being able to efficiently attempt to reduce NOx by lowering the temperature of EGR gas through the EGR cooler.
However, some of the conventional engines have EGR coolers each of which spans above the exhaust-gas converging passage wall (exhaust manifold) (for example, see Japanese Patent Public Disclosure No. 2000-8973). Therefore, it has caused problems.
The conventional engine has the following problems.
<Problem> The EGR Cooler is Readily Damaged.
The EGR cooler receives the heat radiated from the exhaust-gas converging passage wall to be overheated with the result of being damaged with ease.
<Problem> The EGR Cooler Becomes Larger.
Due to the fact that the EGR cooler receives the heat radiated from the exhaust-gas converging passage wall, it is required to enhance its cooling ability so as to remove the heat. This results in enlarging the EGR cooler.